Radio Frequency Identification (RFID) tags attached to objects are primarily used for automatic identification. RFID tags can be active, passive or semi-passive. Active and semi-passive tags have a battery or source of power while passive tags use power harvested from received RF signal. RFID readers are devices that interrogate RFID tags using encoded RF signals. RFID tags respond to query from a reader with a unique identifier that is meaningful to the reader of the tag. RFID tags can also be classified as read/write or read-only tags. Read-Only tags respond back with the same information when queried by a reader. Read-Write tags change the information in response to a query.
Various other references to the prior art and its associated problems are made throughout the following description.
The present invention aims to locate a tag attached to a user or object accurate to a few centimeters. Such an RFID tag has potential for driving many applications where indoor location accuracy is necessary without the use of GPS and cheap enough to be quickly deployed on hundreds of objects.
Each object is to be read disjunctively with the object of at least providing the public with a useful choice.
The present invention aims to overcome, or at least alleviate, some or all of the aforementioned problems.